Electric machines, motors or generators, are well known in the art. It is also widely known that electric machines generate heat as a by-product and that this heat must be somehow extracted from the machine to improve the performance of the machine and/or prevent early degradation or failure thereof.
Electric machines are often air-cooled. This is generally done by providing apertures in the body of the machine to force air therethrough. The efficiency of such a cooling arrangement is generally poor since air is a generally low efficiency cooling fluid. Furthermore, some electric machines operate in environments that are such that it is not possible to provide apertures to allow air therein. Accordingly, fluid cooling arrangements for electric machines have also been designed.
Some permanent magnet electric machines are provided with an internal stator and an external rotor generally enclosing the stator. When this is the case, the stator has a generally cylindrical body and coils are so mounted to the cylindrical body as to outwardly produce a magnetic field that interacts with the externally provided rotor. Since the heat is generally generated in the stator that is somewhat enclosed by the rotor, it may be difficult to install a fluid cooling arrangement inside an enclosed stator of such an external rotor electric machine.